
class Solution {
    public int numDecodings(String s) {
        int n = s.length();
        int[] f = new int[n + 10];
        f[0] = 1;
        for(int i = 1; i <= n;i ++)
        {
            if(s.charAt(i - 1) != '0') f[i] = f[i - 1]; //单独解码s[i - 1]
            if(i >= 2)
            {
                int t = (s.charAt(i - 2) - '0') * 10 + s.charAt(i - 1) - '0';
                if(t >= 10 && t <= 26) f[i] += f[i - 2]; //将s[i - 2] 和 s[i - 1]组合解码
            }
        }
        return f[n];
    }
}

public class lc91 {
}
